Infestation of parasitic rhizocephalan barnacles <i>Sacculina beauforti</i> (Cirripedia, Rhizocephala) in edible mud crab, <i>Scylla olivacea</i>

Screening of mud crab genus Scylla was conducted in four locations (Marudu Bay, Lundu, Taiping, Setiu) representing Malaysia. Scylla olivacea with abnormal primary and secondary sexual characters were prevalent (approximately 42.27% of the local screened S. olivacea population) in Marudu Bay, Sabah. A total of six different types of abnormalities were described. Crabs with type 1 and type 3 were immature males, type 2 and type 4 were mature males, type 5 were immature females and type 6 were mature females. The abdomen of all crabs with abnormalities were dented on both sides along the abdomen’s middle line. Abnormal crabs showed significant variation in their size, weight, abdomen width and/or gonopod or pleopod length compared to normal individuals. The mean body weight of abnormal crabs (type 1–5) were higher than normal crabs with smaller body size, while females with type 6 abnormality were always heavier than the normal counterparts at any given size. Sacculinid’s externa were observed in the abdomen of crabs with type 4 and type 6 abnormalities. The presence of embryos within the externa and subsequent molecular analysis of partial mitochondrial COI region confirmed the rhizocephalan parasite as Sacculina beauforti. Future in-depth descriptions of the life cycle and characteristics of S. beauforti are recommended as it involves a commercially important edible crab species and the effect on human health from the consumption of crabs is of crucial concern

Impact of COVID-19 on aquaculture sector in Malaysia: Findings from the first national survey

Abstract Malaysian aquaculture sector consists of 391,000 t of cultivated organisms produced per year with an economic value for over USD 700 million as estimated in 2019. The COVID-19 pandemic caused a large global human pandemic and it is currently ongoing, affecting profoundly Malaysian aquaculture, which is vital for seafood provision and security assurance. Thus, to increase our understanding about how the pandemic affects aquaculture sectors is crucial to design possible management measures both at local and national level. To do it, we designed a survey, starting in May 2020, consisting of 25 online questions to collect information about the impact of COVID-19 on the aquaculture sectors in Malaysia. A total of 105 respondents (2625 answered questions) was captured within the Movement Control Order (MCO) period and later extended to the Conditional MCO (CMCO). Almost 90 % of respondents was unanimous in answering that, and COVID-19 had a heavy effect on aquaculture-related activities in Malaysia; 80 % of them indicated the market demand and logistic bottlenecks (72 %) as major constraints on their aquaculture activities. While the major option to solve aquaculture COVID-19 related issues was the use of online market or digital platforms (76 %), a large fraction of respondents requested for specific assistance to support aquaculture activities (e.g. financial support). Most respondents (93 %) was aware about the necessity of the Standard Operation Procedure (SOP) provided by the relevant agencies during the MCO / CMCO. Present data are crucial to develop policy measures both at national and international level to support seafood sectors under pandemic

Machine learning with multistage classifiers for identification of of ectoparasite infected mud crab genus Scylla

Recently, the mud-crab farming can help the rural population economically. However, the existing parasite in the mud-crabs could interfere the long live of the mud-crabs. Unfortunately, the parasite has been identified to live in hundreds of mud-crabs, particularly it happened in Terengganu Coastal Water, Malaysia. This study investigates the initial identification of the parasite features based on their classes by using machine learning techniques. In this case, we employed five classifiers i.e logistic regression (LR), k-nearest neighbors (kNN), Gaussian Naive Bayes (GNB), support vector machine (SVM), and linear discriminant analysis (LDA). We compared these five classfiers to best performance of classification of the parasites. The classification process involving three stages. First, classify the parasites into two classes (normal and abnormal) regardless of their ventral types. Second, classified sexuality (female or male) and maturity (mature or immature). Finally, we compared the five classifiers to identify the species of the parasite. The experimental results showed that GNB and LDA are the most effective classifiers for carrying out the initial classification of the rhizocephalan parasite within the mud crab genus Scylla

Characterization of molting stages in the giant freshwater prawn, Macrobrachium rosenbergii using setagenesis of pleopod

This paper characterizes the molting stages of giant freshwater prawn, Macrobrachium rosenbergii under laboratory conditions. Using the distal fifth pleopod as the main reference region and applying Drach’s classification system, we checked the epidermis and carapace hardness and documented major structural changes, such as the retraction of epidermal tissues from the cuticle and setal development. Our findings showed that in early postmolt, no development of seta matrix was observed. A closer examination of seta lumen during the intermolt stage showed that the epidermis was a densely granular structure and the internal cone was developed. In the premolt stage, a retraction of the epidermis from the cuticle (apolysis) and the formation of new seta were recorded. This study shows that using internal seta development changes is apparently a useful, easy, and practical method of determining molting stage in order to facilitate the study of molt-linked processes and metabolism

Immune and bacterial toxin genes expression in different giant tiger prawn, Penaeus monodon post-larvae stages following AHPND-causing strain of Vibrio parahaemolyticus challenge

Acute Hepatopancreatic Necrosis Disease (AHPND), a disease caused by Vibrio parahaemolyticus (V-PAHPND), kills Penaeid shrimps worldwide, resulting in severe economic losses during aquaculture. To further understand how Penaeus monodon post-larvae (PL) respond towards infection of this pathogenic bacterium, the expression of several important immune and bacterial toxin genes in three stages of P. monodon PL (PL15, PL30 and PL45) upon V-PAHPND challenge, were determined. A 20-hrs challenge test with 2.7 x 10(7) cfu ml(-1) of V-PADPND resulted 81, 65 and 1.7% mortality respectively for PL30, PL15 and PL45, indicating that PL30 was most vulnerable to V-PADPNEP The immune response of shrimp PL at this stage was robust, with Toll-like receptor (TLR), prophenoloxidase (proPO), lysozyme (lyso) and penaeidin (PEN) augmented approximately 10.7, 4.7, 6.5 and 3.2-fold, respectively. The expression initiated at one hour post-infection (h.p.i), peaked at 16 h.p.i and 20 h.p.i, and decreased at 18 h.p.i, indicating the crucial involvement of these immune related genes in the defence and recovery of the first-line defence mechanisms during V-PADPND infection. This work also revealed that toxR gene represents a good indicator gene for Vibrio detection whereas PIR A, for V-PADPND pathogenicity determination of P. monodon. Overall, these findings provided novel insights into the immune response and V-PADPND No susceptibility of different P. monodon PL stages during infection, with outcomes potentially useful in enhancing the application of health therapy and biosecured aquaculture practices to minimize the damaging risk of AHPND towards sustainable production of P. monodon

Live foods for juveniles production of blue swimming crab, Portunus pelagicus (Linnaeus, 1766)

The study were aim to demonstrate the affects of live food type’s i.e., mixed diatom, Artemia nauplii and rotifer on survival rate and molt time of larvae stage till 1st day juvenile crabs (C1) of P. pelagicus. Three types of feeding regimes given to the crab larvae through out the study trials are with and without mixed diatom, with and without Artemia nauplii and with and without rotifer. The study shows that zoea fed with rotifer alone was not enough to sustain survival in the next zoea stages and to promote metamorphosis up to megalopa stage. Survival of zoea fed with Artemia nauplii alone shows that this type of food is not suitable for the very early zoea stages. The study also shows that the adding of mixed diatom to larvae rearing system where rotifer and Artemia nauplii is main food items did not produced high survival rate as compared to larvae rearing fed on rotifer and Artemia nauplii alone. The results of the study demonstrated that the food types not only effect survival rate but also the growth of crab larvae. The study generally ended that the combination diet of rotifer and Artemia nauplii alone is enough to produced C

Relationship between the carapace width and body weight increments and the confirmation of Stage 1 ovary after molting of the immature orange mud crab, Scylla olivacea, (Herbst, 1796) in captivity

This study describes the relationships between the carapace width (CW) and body weight (BW) increments and the confirmation of Stage 1 ovary after the molting of immature orange mud crabs, Scylla olivacea, in captivity. Morphological coloration and histological assessments were done on 165 immature female S. olivacea. Healthy crabs were sampled from the Setiu Wetlands in the coastal waters of Terengganu on the Malaysian Peninsula from July to September 2015. Thirty crabs were sacrificed for a preliminary study as a standard (control) in which the gonads (if available) were dissected for histological study. The remaining crabs (n=135) were selected for subsequent analysis (limb autotomy). Compared to the controls, the molted crabs generally did not produce any difference in the stage of the ovaries (remaining in Stage 1) but were observed to have larger oocytes. This demonstrated that the limb autotomy technique may activate hormone regulation, thus triggering vitellogenesis in the mud crab. There were also positive correlations between CW and BW (P=0.001, P<0.01) and significant differences through regression analysis (P=0.002, P<0.01) with the equation y = 2.61x + 6.27 (R2=0.069). These results can be useful for developing baseline data for further crab management in Malaysia

Biochemical changes of cryopreserved seminal plasma and spermatozoa of the giant grouper Epinephelus lanceolatus after preservation and transportation using dry-ice

The present study aims to investigate the effects of exposure of the seminal plasma and spermatozoa of the giant grouper Epinephelus lanceolatus to dry ice ( 79 C) during transport on their quality. In all, 15 amino acid compounds were determined. The quantification of total proteins were measured using the Bradford method, and amino acid concentration were measured using the HPLC method. The cryopreserved seminal plasma was transferred from a liquid nitrogen tank to a styrofoam box filled with dry ice. Total protein and amino acids were measured after 24, 48, and 72 h. For comparative purposes, total protein and fifteen compound of amino acid were also measured. Both parameters were also measured after the cryopreserved seminal plasma were immersed in liquid nitrogen after 24 and 48 h exposed to dry ice. The results showed that the exposure of seminal plasma to dry ice for 24, 48 and 72 h during transportation or immersion back into the liquid nitrogen after 24 and 48 h does not change the total protein levels either in seminal plasma or spermatozoa. However, the level of each amino acid compound in the seminal plasma had significantly decrease

Testis maturation stages of mud crab (Scylla olivacea) broodstock on different diets

The aim of this study was to investigate how various diets influence testis maturation stages in mud crab (Scylla olivacea) broodstock. Morphological and histological assessments were performed in triplicate (10 male crabs each). Daily, subject crabs were fed a squid (Loligo sp.) and a fish (Decapterus sp.) diet at 5-10% of body weight. Diets were analyzed following methods from the Association of Analytical Communities (AOAC). In comparison to control (wild) crabs, the two diets generally did not cause significant differences (p>0.05) in body weight, carapace width and gonadosomatic index (GSI), except in the GSI of squid-fed crabs (p<0.05). At the end of the experiment, crabs that reached Stage 3 testis maturation included were 6 fish-fed individuals and 23 squid-fed individuals. Additionally, differences in crude protein and fat levels across diets influenced the nature of male gonadal development. In conclusion, a squid diet was sufficient to induce Stage 3 testis maturation in Scylla olivacea within 60 days of culture. Our results prove the usefulness in developing appropriate feeding regimes for male Scylla olivacea broodstock

The potential of bioflocculant-producing bacteria as inoculum for biofloc based systems

Aim: Biological flocculants has been widely used around the world to replace the usage of synthetic flocculants for wastewater treatment.Anew green technology using biological flocculant known as biofloc system was developed which offers zero water exchanged, low feed conversion ratio (FCR) and high nutritional profile. This study was conducted to determine the most potential bioflocculant-producing bacteria isolated from biofloc sampleinPacific Whiteleg shrimp,P. vannameiculture pond. Methodology: Biofloc sample was collected using Imhoff cone and bacteria was isolated. The most abundant bacteria isolated throughout P. vannamei culture period was selected for screening of bioflocculant-producing bacteria usingYPG medium and flocculation activity using floc-jar test. Results: Screening of bioflocculant-producing bacteria showed that B. infantis, N. aquimarinus, B. cereus, H. venusta, Pseudoalteromonas sp., and B. safensis were characterized as highly mucoid and ropy colony morpologies. The highest flocculation activity with 93% was showed by B. infantis followed by N. aquimarinus (91%), B. cereus (87%), H. venusta (79%), Pseudoalteromonas (78%), while the lowest flocculation activity was showed byB. safensiswith 69%. Interpretation: As bacteria grew, extracellular polymeric substances (EPS) produced were involved in flocculation process. Each bacteria produced different EPS composition which differed their ability in flocculation process. Therefore, bacteria with high flocculation activity are potentially used as inoculum to increase flocculation processinbiofloc production